The large, rose stained structure shown in the image is

• A. A neuron
• B. A synapse
• C. A glial cell
• D. An axon

Answer: (A)

When a tissue is stained with a rose-colored stain like cresyl violet (a Nissl stain), neuronal cell bodies stand out because they contain abundant rough endoplasmic reticulum, known as Nissl substance. This material binds the stain and creates a large rose-colored region within the soma, which also houses the nucleus and nucleolus. Glial cells are smaller and have less cytoplasm with far less conspicuous Nissl substance, so they don’t appear as a prominent rose-stained blob. Axons are slender fibers and lack Nissl bodies, so they wouldn’t appear as a large rose-stained structure. Synapses are connections, not whole cell bodies, and wouldn’t present as this large rose-stained structure either. So the large rose-stained structure observed is the neuron's cell body (soma).